okay, first: they HAVEN'T identified the length or method of transmissability, because it keeps spreading by surprise.
second: we know that in Africa they have missed many cases. Therefore, 7000 actual cases would not be far off.
Third, the world population is 7 million, so there are 2^20 doublings (at 23 days each) between now and total infection, at the current rate.
Fourth, the US population, including illegals, is about 350 million. So by the math, you might guess that there was 350 cases in the US, but the actual rate of spread is probably initially faster than a 23-day doubling, but slower to enter the country. So a reasonable guestimate is that we might have 120 cases, about a third of 350, but with Dallas/CDC response, we'll rapidly catch that 350 number.
In line with that, I'd estimate that in any state that has a lot of human commerce with Dallas (including Louisiana, Virginia, Oklahoma, and California), you could estimate the number of cases by dividing the state population by 3 million, more or less.
In other words, we're in deep trouble already.